The present invention relates to a method for microwave plasma processing wherein the method for applying bias to the sample in a plasma processing method such as dry etching and deposition using microwave plasma is improved, particularly to a plasma etching method suitable for increasing etch rate, improving etching accuracy, improving selectivity to the underlying material, removing the surface oxide films of a material to be etched, and/or reducing damage given to the elements in the sample.
It is known that the conventional microwave plasma processing apparatus is provided with means for applying a radio-frequency bias voltage to the sample to be processed in order to improve processing effect, as described, for instance, in the Japanese Patent Publication No. 37311/1981 official gazette. However, the above-mentioned radio-frequency bias voltage is always applied during plasma processing. In etching, for instance, the radio-frequency bias voltage is always applied to the sample during the time etching and over-etching are being carried out, and consideration is not given at all to the resulted reduction of etching selectivity to the underlying material on which a layer of the material to be etched is formed, or to the resulted occurrence of damage of the underlying material and damage accompanying it.